Various methods for containing fuel in an aircraft involve the use of a rigid tank. To thermal insulate cold fuel from a hot airframe structure, insulating material, typically comprising rigid insulation, is disposed on the exterior surface of a fuel tank or internal surface of the vehicle structure in the form of a thermal protection system. Application of the insulation typically requires a complex supporting structure to prevent the insulation from buckling or failing. Thermal insulation of fuel, therefore, is typically accomplished by containing the fuel in a rigid structure and applying insulating materials to the exterior of the structure. The necessity of a rigid structure inevitably increases the complexity and structural weight of the aircraft.
Alternatively, when cold fuel is disposed in a hot airframe structure without thermal decoupling, the airframe structure must be sized to accommodate the thermally induced stresses caused by the containment of the cold fuel. Accommodation of the thermally induced stresses typically requires increasing the size of the airframe structure, which inevitably increases the structural weight of the aircraft.